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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [LLVM-COV] Wrong coverage when using fork() to create a new process"
href="https://bugs.llvm.org/show_bug.cgi?id=41051">41051</a>
</td>
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<tr>
<th>Summary</th>
<td>[LLVM-COV] Wrong coverage when using fork() to create a new process
</td>
</tr>
<tr>
<th>Product</th>
<td>Runtime Libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>libprofile library
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yangyibiao@nju.edu.cn
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>$ clang -v
clang version 9.0.0-svn352319-1~exp1+0~20190127174513.767~1.gbp29cf87 (trunk)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Candidate multilib: .;@m64
Selected multilib: .;@m64
$ cat small.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
int main(int argc, char *argv[]) {
printf("hello world (pid:%d)\n", (int) getpid());
int rc = fork();
if (rc < 0) { // fork failed; exit
fprintf(stderr, "fork failed\n");
exit(1);
} else if (rc == 0) { // child (new process)
printf("hello, I am child (pid:%d)\n", (int) getpid());
} else { // parent goes down this path (main)
printf("hello, I am parent of %d (pid:%d)\n", rc, (int) getpid());
}
return 0;
}
$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=small.profraw
small.c; ./a.out; llvm-profdata merge small.profraw -o small.profdata; llvm-cov
show a.out -instr-profile=small.profdata small.c > small.gcov; cat small.gcov
hello world (pid:170848)
hello, I am parent of 170849 (pid:170848)
hello, I am child (pid:170849)
1| |#include <stdio.h>
2| |#include <stdlib.h>
3| |#include <unistd.h>
4| |#include <sys/wait.h>
5| |
6| 2|int main(int argc, char *argv[]) {
7| 2| printf("hello world (pid:%d)\n", (int) getpid());
8| 2| int rc = fork();
9| 2| if (rc < 0) { // fork failed; exit
10| 0| fprintf(stderr, "fork failed\n");
11| 0| exit(1);
12| 2| } else if (rc == 0) { // child (new process)
13| 1| printf("hello, I am child (pid:%d)\n", (int) getpid());
14| 1| } else { // parent goes down this path (main)
15| 1| printf("hello, I am parent of %d (pid:%d)\n", rc, (int)
getpid());
16| 1| }
17| 2| return 0;
18| 2|}
Line #6, #7, #8 are wrongly executed twice. Since this is fork a new process.
Thus, these three statements should only executed once.</pre>
</div>
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